ATHLETIC: The novel exercise device for spaceflight enables only partially comparable plyometric training to training on ground

Kurzfassung

Background: The AstronauT HeaLth EnhancemenT Integrated Countermeasure (ATHLETIC) training device was developed, after plyometric training has been shown to be an effective measure to maintain muscle and bone health in a bed rest study. The aim of this study was to test if participants could reach a training load on ATHLETIC comparable to earth conditions within 10 training sessions.

Methods: 8 healthy participants performed Reactive Forefoot Hopping and Countermovement Jumps. After recording reference jumps on a force plate and ATHLETIC, the participants tried to reach a load comparable to body weight equivalent in up to 10 training sessions. To compare the reference and ATHLETIC, we analyzed Ground Contact Times for hopping, the Rate of Force Development for the Countermovement Jumps and Ground Reaction Forces for both using means and standard deviations and applying a mixed model.

Results: Reactive hopping progression was possible (Ground Contact Time decreased from 477 ± 69 ms in PRE to 366 ± 43 ms in Training 4, p < 0.001) but Ground Reaction Force remained below reference values (max. 49.9 ± 7.5%, p < 0.001). Progression for the Countermovement Jumps was faster, with the Rate of Force Development significantly increasing (PRE: 2.2 ± 1.1 kN, Training 3: 6.1 ± 1.1 kN, p < 0.001). Ground Reaction Force during landing (Max. 38.5 ± 13.6% of reference in Training 5, p < 0.001) did not reach reference values. Due to a defect of ATHLETIC we had to end the study prematurely.

Discussion and Conclusions: The training load could only be partially recreated on ATHLETIC. The reduced load on ATHLETIC might be a result of friction in the system. Even though the load is reduced, it might provide sufficient training stimulus. However, if ATHLETIC is to be pursued further, faster movements, durability and reparability need to be enabled and tested during bed rest and parabolic flight.